Comparison of Iris L. morphogenesis in in vitro culture with seedling development in some highly specialized plants

A sharp change in the course of ontogenesis and transition to another type of nutrition (parasitic nutrition) is supposed to contribute to similarity of the morphogenetic processes in in vitro plants and seedlings of higher parasitic plants. Tracheary elements are formed in the shoots of Iris in in vitro culture as an adaptive response of the plant body to culture conditions. Underdevelopment of the vascular system for transporting nutrients from the agar medium to plant tissues results in the formation of this vascular system in the maternal shoots. Macronutrients and plant hormones are transported to the zones of meristematic activity via the vascular system. Parasitic plants obtain nutrients from their hosts through the newly formed vascular system. The elements of tracheary structures are unique for haustoria and play a vital role not only in deposition and transport of macronutrients, but also in the hydrostatic pressure regulation and protection against pathogens. The vascular system of parasitic plants is disordered similar to that of regenerated plants. This vascular system can be referred to as a distribution network, the structure capable of transforming a set of cells into the cellular transport system, which unites tissues and organs into a single growing organism.